1. Field of the Invention
The present invention relates to electric equipment and a method for controlling the same, and more particularly, to electric equipment that has a digital interface and a method for controlling the same.
2. Description of the Related Art
In recent years, HDMI (High-Definition Multimedia Interface) has been used as a digital interface for equipment that handles high definition video, multi-channel audio and so on. The devices connected with an HDMI can recognize the type or the like of the other device and, therefore, they can not only transfer video and audio signals via a connection cable, but can also control the other device and operate in conjunction with the other device.
FIG. 14 is a diagram showing a communication configuration of a system in which a TV receiver, a repeater device such as an AV (Audio Visual) amplifier, and a recording device such as a hard disk recorder are connected with an HDMI.
The details of the communication between pieces of equipment that are connected with an HDMI can be found in HDMI Licensing, LLC, “High-Definition Multimedia Interface Specification Version 1.3a”, Nov. 10, 2006.
A procedure for acquiring a physical address of a repeater device 1402 will be described first. When the repeater device 1402 brings a 5VPWR (+5V power) line of an HDMI output terminal 14023 to a high voltage level, a TV receiver 1401 brings an HPD (Hot-Plug Detect) line of an HDMI input terminal 14013 to a high voltage level. By doing so, the repeater device 1402 recognizes that it is capable of DDC (Display Data Channel) communication with the TV receiver 1401. Subsequently, the repeater device 1402 acquires a physical address from an EDID (Extended Display Information Data)-ROM 14012 of the TV receiver 1401 through DDC communication.
A DDC is a standard defined by the VESA (Video Electronics Standards Association). A DDC is a channel for providing information regarding a display stored in the EDID-ROM on the display side to equipment that transmits display data to the display. The physical address of the TV receiver 1401 is a fixed physical address of 0.0.0.0. The physical address of the repeater device 1402 is specified in the EDID-ROM 14012 provided for each HDMI input terminal of the TV receiver 1401, and can be, for example, 1.0.0.0.
Similarly, a physical address of a recording device 1403 is also acquired from an EDID-ROM 14022 of the repeater device 1402 through DDC communication. The physical address of the recording device 1403 is specified in the EDID-ROM 14022 provided for each HDMI input terminal of the repeater device 1402, and can be, for example, 1.1.0.0.
Next, a method for acquiring a logical address will be described. As shown in FIG. 2, a logical address that can be acquired is preset for each device type.
For example, a recording device can acquire one of “1”, “2” and “9”, and an audio system (the repeater device 1402 in FIG. 14) can acquire “5”. In this manner, the upper limit for the number of logical addresses that can be assigned is set for each device type.
The recording device 1403 broadcasts a Polling message to a logical address (e.g., “1”) that the recording device 1403 wants to acquire. If there is no response to the Polling message from any other device (if a message with ACK bit=1 is returned), the recording device 1403 can recognize that the logical address is unoccupied, so it acquires the logical address. If, on the other hand, there is a response from another device (if a message with ACK bit=0 is returned), it means that the logical address has already been acquired by another recording device. In such a case, the recording device 1403 repeats the same process for other available logical addresses (e.g., “2” and “9”) to acquire a logical address (see, for example, Japanese Patent Laid-Open No. 2007-202115 and the above-mentioned “High-Definition Multimedia Interface Specification Version 1.3a”).
Usually, when connecting two devices via a repeater device, as shown in FIG. 14, the HDMI input terminal of a first device (TV receiver 1401) is connected to the HDMI output terminal of the repeater device 1402, and the HDMI output terminal of a second device (recording device 1403) is connected to the HDMI input terminal of the repeater device.
However, as the HDMI input terminal and the HDMI output terminal of the repeater device appear the same, a situation can occur in which the user erroneously connects input terminals or output terminals.
FIG. 1 is a diagram showing a state in which the input terminals, as well as the output terminals, are erroneously connected when connecting devices as in FIG. 14.
Specifically, in FIG. 1, an HDMI input terminal 1024 of a repeater device 102 and an HDMI input terminal 1013 of a TV receiver 101 are erroneously connected, and an HDMI output terminal 1023 of the repeater device 102 and an HDMI output terminal 1032 of a recording device 103 are erroneously connected.
When erroneously connected as just described, the repeater device 102 and the recording device 103 cannot acquire a physical address and a logical address, remaining in a state in which CEC (Consumer Electronics Control) communication is not possible. Specifically, even when the repeater device 102 brings the 5VPWR line of the HDMI output terminal 1023 to a high voltage level, the repeater device 102 cannot acquire a physical address from an EDID-ROM 1012 of the TV receiver 101. This is because the HDMI output terminal 1023 of the repeater device 102 is not connected to the HDMI input terminal 1013 of the TV receiver 101, but is connected to the HDMI output terminal 1032 of the recording device 103.
In addition, because the input terminals, as well as the output terminals, are connected to each other, it is not at all possible to exchange data between the devices.
However, there has not been a system for notifying a user of the occurrence of such an erroneous connection between input terminals or between output terminals, so such conventional technology is not user friendly. In particular, it has been difficult for a user who is inexperienced in the operation of electric equipment to understand what has gone wrong.